Field of the Invention
The present invention relates to a part including a structure.
Description of the Related Art
In certain applications, a structure is subjected to aerodynamic stresses caused by the flow of a fluid, e.g. air, around said structure. This applies for a structure that is a part of an aviation turbine engine, e.g. a fan blade. These stresses can cause the structure to vibrate. Such a structure also possesses its own vibration modes associated with its mechanical properties (essentially its distributions of stiffness and mass). Unstable coupling can then become established between the vibration generated in the structure by the aerodynamic stress, and the vibratory characteristics of the structure, by feedback between the structure and the fluid that flows around it. This coupling phenomenon is known as “flutter”. Whether or not flutter appears in a structure that is subjected to aerodynamic stresses depends on the balance of the sum of two energies: the aerodynamic energy EA and the mechanical dissipation energy of the structure EM.
The aerodynamic energy EA is the energy transmitted by the fluid to the structure as a result of flowing around it.
The mechanical dissipation energy of the structure EM is the energy that is dissipated mechanically by the structure. This dissipation depends on the intrinsic mechanical properties of the structure. For a structure made of composite material, these mechanical properties depend on the nature of the materials making up the composite structure, and on the internal architecture of the structure, i.e. on the arrangement between the various materials that make it up. This arrangement may exist at one or more scales: mesoscopic (short/long fibers, particles), macroscopic (weaving, braiding, layers/plies).
There is a risk of flutter in the structure when (−EA)>EM.
Flutter is a phenomenon that is undesirable in a structure since it causes the structure to enter into resonant modes in which vibration amplitudes within the structure increase in uncontrolled manner, and that can lead to the structure being destroyed.
The present invention seeks to remedy that drawback.